Filter device, in particular return line suction filter, and filter element for use in such a filter device

ABSTRACT

The invention relates to a filter device, in particular a return line suction filter, having at least one filter housing ( 3 ) in which a filter element ( 17 ) defining a longitudinal axis in the form of a filter cartridge can be received and comprises an enclosure at at least one end thereof for the corresponding end cap ( 21 ) forming the end edge of the filter material ( 39 ) and that can be fixed to an element receptacle ( 5 ) connected to the filter housing ( 3 ) for fixing the location of the filter element ( 17 ) in the functional position thereof, characterized in that the element receptacle ( 5 ) and the associated end cap ( 21 ) of the filter element ( 17 ) have design irregularities ( 63, 65 ) adapted to each other at the parts thereof ( 23, 47 ) engaging each other in the functional position of the filter element ( 17 ), said irregularities enabling the engagement in a positional alignment to each other.

The invention relates to a filter device, in particular a return line suction filter, having at least one filter housing, in which at least one filter element which defines a longitudinal axis in the form of a filter cartridge can be accommodated, which cartridge on at least one end has an end cap which forms an enclosure for the pertinent end edge of the filter material and which can be fixed on an element receptacle which is connected to the filter housing for fixing the filter element in its operating position. Moreover, the invention relates to a filter element for such a filter device.

Filter devices of this type are readily available commercially in different designs. To a large extent, these filter devices are used for filtration of working fluids, such as hydraulic fluids, fuels, lubricants, and the like. Such a device in the form of a suction filter is described, for example, in brochure D7.108.2/06.07 of the applicant with the product description of RKM return line suction filter and is commercially available in different pressure stages (up to 10 bar) and for different return volumetric flows (up to 800 l/min).

Return line suction filters are used in hydraulic systems in those cases in which there are both an open hydraulic circuit (for example, working hydraulics) and also a closed hydrostatic system (for example, traction drive) in the system. In this connection, return line suction filters can perform both the function of the return line filter of the open circuit and also the function of the suction filter of the closed circuit (drive), provided that the return flow of the open hydraulic system is not less than the volumetric flow of the feed pump for the hydrostatic system. In fluid systems, specifically hydraulic systems, in which filter devices are used, the operating reliability of the system depends largely on the reliable operation of the filter device located in the system. In other words, failure of the filter device, beyond the failure of the pertinent system, can lead to serious damage to the system and thus can cause significant financial losses.

With respect to this problem, the object of the invention is to make available a filter device which is characterized by special operating reliability.

This object is achieved according to the invention by a filter device which has the features of claim 1 in its entirety.

According to the characterizing part of claim 1, an important particularity of the filter device consists in that design irregularities are formed both on the element receptacle of the pertinent filter housing and also on parts of the end cap of the filter element which is assigned to the element receptacle, the design irregularities on the element receptacle and on the end cap being matched to one another such that if they are aligned to one another, they enable mutual engagement. Since in this way a pertinent filter element can be moved into the operating position only under the assumption that complementary design features on the element receptacle and end cap are matched to one another such that they allow the engagement with the corresponding mutual alignment, it is ensured that the filter device can be operated only with a filter element which is intended for a respective special use and which satisfies the pertinent applicable specifications ensuring operating reliability.

Thus it is not only precluded that a filter element will be used which has an unsuitable filter fineness or which is not suitable for the respective application, that is to say, is not assigned to a corresponding pressure stage, but that the risk will also be avoided that possibly a so-called “low-end element” available on the market will be used which does not meet the applicable safety standards.

Since, to enable mutual engagement, a positional relation is necessary in which the design irregularities have a positional relation aligned to one another, there is the additional advantage that the engagement between element receptacle and end cap forms a locking element so that even for a tangential flow occurring in a filter housing, the filter element is supported against a possible torque around the longitudinal axis.

In preferred exemplary embodiments, the filter housing has the shape of a cup, from whose top the filter element can be inserted and which can be fixed on the element receptacle, forming a housing bottom part. In filter housings with this type of design, a housing cover typically forms the upper termination of the housing and a support for the upper end cap of the filter element. Accordingly, the housing cover can be screwed to the top end of the filter housing or bolted to it, only if the filter element is properly engaged with the element receptacle on the bottom part of the housing. An attempt to inadvertently install an “incorrect” filter element is thus immediately conspicuously indicated to the operator.

Here the arrangement can preferably be made such that the bottom part, which forms the element receptacle, has a pipe socket which projects coaxially from its top and which extends into the inner filter cavity of the filter element that is in the operating position to form a fluid connection, the pipe socket on the outer peripheral side having the design irregularities which belong to the element receptacle.

To fix the filter element on an element receptacle designed in this way, the end cap can have a coaxial connector which extends into the inner filter cavity surrounded by a fluid-permeable support pipe and which is engaged by the pipe socket of the element receptacle in the operating position of the filter element. The design irregularities which belong to the end cap are located on the inner wall of the connector of the end cap.

In especially advantageous exemplary embodiments, the design irregularities on the pipe socket of the element receptacle have at least one radially projecting rib which runs in the longitudinal direction and to which a depression is assigned which extends in the longitudinal direction in the inner wall of the connector of the end cap.

There is especially effective protection against confusion when there are several longitudinal ribs which are distributed around the periphery of the pipe socket of the element receptacle and several depressions assigned to the ribs in the connector of the end cap, and for this reason, depending on the distribution pattern of the arrangement of the ribs and depressions, only specially adapted filter elements can be used.

In advantageous exemplary embodiments, the end cap is composed of an inner sleeve body which is concentric to the longitudinal axis, which forms the inner wall of the connector with the depressions located in it, and which is integral with a peripheral annular member which forms the enclosure for the end edge of the filter material, and of an outer sleeve which surrounds the sleeve body and whose outside forms a contact surface for the support pipe of the filter element. This two-part construction of the end cap is advantageous with respect to production with press-molded plastic parts.

If, in this connection, the arrangement is made such that the outer sleeve forms a hollow cylinder whose axial length is greater than that of the inner sleeve body, so that the inner end edge of the outer sleeve projects over the end edge of the sleeve body and that the end edge of the outer sleeve forms an end part which is drawn radially to the inside, this end part together with the adjacent end edge of the sleeve body can border an annular groove-like space which is used as a seat for an annular sealing element. This execution of the end cap thus enables perfect sealing of the inner filter cavity on the bottom part of the housing and thus sealing of the inner filter cavity which forms the clean side in the filter process relative to the dirty side which is located on the outside of the filter element.

Preferably, the bottom part which forms the element receptacle on the bottom which faces away from the pipe socket forms a valve housing part which is integrally molded on and which has an outlet which can be connected to the tank side of a hydraulic system. In this way, a bypass valve and valve arrangements as are used, for example, in return line suction filters can be easily integrated mechanically into the bottom part.

In this respect, in the bottom part there can be a first fluid passage which leads to a bypass valve located in the valve housing from the dirty side of the filter element which is in the operating position, bypassing the pipe socket, and there can be a second fluid passage which leads from the pipe socket to at least one other valve located in the valve housing, such as an anti-cavitation valve and/or back pressure valve, which valve or valves is or are connected to the outlet.

The subject matter of the invention is also a filter element for use in a filter device according to one of claims 1 to 10, the filter element having the features of claim 11 in its entirety.

The invention is detailed below using one exemplary embodiment which is shown in the drawings.

FIG. 1 shows a longitudinal section of one exemplary embodiment of the filter device according to the invention, the state being shown in which an attempt is made to bring a filter element that is not suitable for use into the operating position in the filter housing;

FIG. 2 shows a longitudinal section which is drawn on a slightly smaller scale than FIG. 1, the state being shown in which a filter element is in the operating position;

FIG. 3 shows a partial extract of the region designated as III in FIG. 2, drawn on a larger scale than FIG. 2;

FIG. 4 shows a perspective oblique view of only the housing bottom part of the exemplary embodiment, which forms an element receptacle;

FIG. 5 shows a perspective oblique view of a filter element which is intended for use in the device according to the invention, viewed looking at its end cap which interacts with the element receptacle;

FIG. 6 shows a partial front view of only the region designated as VI in FIG. 5, drawn on a larger scale than FIG. 5, and

FIGS. 7 a to 7 c show longitudinal sections of only the parts of the end cap of the filter element which interact with the element receptacle of FIGS. 5 and 6, FIG. 7 c showing the end cap in the assembled state.

A filter housing, which is designated as a whole as 1, has a hollow cylindrical main part 3 which on its bottom side end is sealed by a housing bottom part 5. The upper end of the main part 3 is adjoined by a housing top part 7 which in the manner conventional for these filter housings has fluid guides, of which the drawings show a fluid inlet 9 via which fluid to be cleaned can be supplied to the space in the filter housing 1 which forms the dirty side in the filter process. Another fluid guide, which is provided in the top part 7 and which is connected to the space which forms the clean side in the filter process, leads to an outlet for the emergence of cleaned fluid from the housing top part 7, this outlet not being shown in the drawings since it is turned by 90 degrees relative to the plane of the drawings. On the top end of the housing top part 7, there is an internal thread 11 to which the external thread 13 of a housing cover 15 can be screwed. FIG. 1 shows that the housing cover 15 is in a position raised off the top part 7 and in which the internal thread 11 and external thread 13 do not engage.

The filter housing 1 can accommodate a filter element 17 in the form of a filter cartridge which with the housing cover 15 removed can be inserted into the filter housing 1 from the open end of the housing top part 7 along the longitudinal axis 19. For fixing of the filter element 17 in its operating position, the bottom part 5 forms an element receptacle which interacts with the bottom side end cap 21 of the filter element 17. As the main part of the element receptacle, the bottom part 5 has a pipe socket 23 which projects axially away from the bottom part 5 in the direction to the housing top part 7 and which is concentric to the axis 19. FIG. 1 shows a state in which the filter element 17 with its end cap cannot be slipped far enough onto the pipe socket 23, but is blocked in the position shown in FIG. 1 as a result of the shape of the pipe socket 23. In this position of the filter element 17, the housing top part 7 cannot be closed by the housing cover 5 because the housing cover 15 which adjoins the cover-side end cap 25 of the filter element 17 is held by the housing top part 7 at a distance at which the internal thread 11 and external thread 13 cannot engage.

FIG. 4 shows details of the shaping of the bottom part 5. It is connected by its circular ring-shaped peripheral edge in the form of an annular member 27 to the bottom end of the housing main part 3 such that the bottom end 29 of the main part 3 formed by a steel pipe encompasses the annular member 27 and on the top edge of the annular member 27 a flanged site 31 is formed. In the outer periphery of the annular member 27, there is an annular groove 33 for a gasket 35 for sealing between the bottom part 5 and housing main part 3.

FIGS. 2 to 7 illustrate details of the configuration both of the bottom part 5 and also of the assigned end cap 21 of the filter element 17 which is suitable for use in the filter device. As is apparent from FIGS. 5 to 7, the end cap 21 forms an annulus 37 as enclosure for one end edge of the filter material 39 of the filter element 17, which material surrounds a support pipe 41. The support pipe 41 borders the internal filter cavity which forms the clean side in the filter process in the filter element 17. As FIGS. 7 a to 7 c show, the end cap 21 has a two-part construction, namely from an inner sleeve body 45, which is concentric to the axis 19 and which on its inside forms the inner wall of a concentric connector 47, which projects axially away from the bottom 49 of the annulus 37, into the inner filter cavity 43. The end cap 21 is completed by an outer sleeve 51 which is shown separately in FIG. 7 a and which is slipped over the outside of the connector 47, and, as shown in FIGS. 2 and 3, is in contact on the outside with the support pipe 41. As FIG. 7 c shows, the axial length of the outer sleeve 51 is larger than that of the pipe socket 47 so that the inner end edge 53 of the outer sleeve 51 in the assembled state of FIG. 7 c projects over the end edge 55 of the connector 47. Therefore, the end edge 53, with an end part 57 which is drawn radially to the inside, forms a seat 59 (FIG. 7 c) for a gasket 61, see FIGS. 3 and 2.

As FIG. 4 shows best, on the outer periphery of the pipe socket 23, which forms the main part of the element receptacle of the bottom part 5, radially projecting longitudinal ribs 63 are molded, of which in this example there are four at uniform angular distances and of which two are shown in FIG. 4. To enable the engagement between the connector 47 of the end cap 21 and the pipe socket 23, the inner wall of the connector 47, as design irregularities which are complementary to the longitudinal ribs 63, has depressions 65 in the inner wall of the connector 47. These depressions 65, in complementary arrangement to the longitudinal ribs 63 of the pipe socket 23, make it possible for the filter element 17 with its end cap 21 to be able to be slipped onto the pipe socket 23 until the bottom 49 of the end cap 21 makes contact with spacers 67 (FIG. 4) of the element receptacle and for the filter element 17 to be in its operating position. Here, as FIG. 3 shows best, the inner filter cavity 43 (clean side) is sealed by a gasket 61 relative to the element receptacle on the pipe socket 23.

The depressions 63, see FIGS. 5, 6 as well as 7 b and 7 c, have a greater width in the peripheral direction than the longitudinal ribs 63 on the pipe socket 23 of the element receptacle, so that the longitudinal ribs 63 and the depressions 65 can easily be moved toward one another when the filter element 17 is moved into the operating position, and also the filter element 17 can be removed without obstacles when the element is being changed. Thus the radial travel path produced in this respect can be used to loosen a possibly fixed seal in which the seal is entrained at least some distance of this travel path. This moving together is moreover facilitated by the depressions 65 on the open end, i.e., on the bottom 49 of the end cap 21, each having an arc-shaped widening 69.

It goes without saying that instead of the complementary design irregularities which are formed by longitudinal ribs 63 and depressions 65, there can be differently shaped configurations in any pattern arrangement on the element receptacle (pipe socket 23) and end cap 21. The assignment of radially projecting and radially recessed elements could also be chosen to be the reverse of this example so that, for example, there could be longitudinal ribs on the end cap 21 and depressions on the pipe socket 23 of the element receptacle.

FIGS. 1 to 4 show that the bottom part 5 which forms the element receptacle on its bottom facing away from the pipe socket 23 has a housing part 71 which is molded on in one piece and which together with an outlet part 73 which forms the housing termination forms a valve housing.

The outlet part 73 in turn forms an outlet 75 which can be connected to the tank side of an assigned hydraulic system which is not shown. A fluid passage 77 which is located in the bottom part 5 connects the space 79 of the filter element 17 which is in the operating position, which space forms the dirty side in the filter process, to a bypass valve 81 in the valve housing 71, 73 which enables a pressure decrease from the fluid passage 77 to the tank-side outlet 75 with pressure actuation. When using the exemplary embodiment of the filter device described here as a return line suction filter, within the valve housing 71, 73 and in the fluid connection to the outlet 75, there is another valve arrangement 83 in the form of a combined anti-cavitation valve and back pressure valve which is inserted between a second fluid passage 85 in the bottom part 5, which fluid passage is connected to the inner filter cavity 43 forming the clean side, and the tank-side outlet 75. 

1. A filter device, in particular a return line suction filter, having at least one filter housing (1) in which at least one filter element (17) which defines a longitudinal axis (19) in the form of a filter cartridge can be accommodated, which cartridge on at least one end has an end cap (21) which forms an enclosure for the pertinent end edge of the filter material (39) and which can be fixed on an element receptacle (5) which is connected to the filter housing (1) for fixing the filter element (17) in its operating position, characterized in that the element receptacle (5) and the assigned end cap (21) of the filter element (17) on their parts (23, 47) which engage one another in the operating position of the filter element (17) are provided with design irregularities (63, 65) which are matched to one another and which enable engagement in positional relation aligned to one another.
 2. The filter device according to claim 1, characterized in that the filter housing (1) has the shape of a cup, from whose top the filter element (17) can be inserted and which can be fixed on the element receptacle forming a housing bottom part (5).
 3. The filter device according to claim 2, characterized in that the bottom part (5) which forms the element receptacle has a pipe socket (23) which projects coaxially from its top and which extends into the inner filter cavity (43) of the filter element (17) located in the operating position to form a fluid connection, and that the pipe socket (23) on the outer peripheral side has the design irregularities (63) which belong to the element receptacle.
 4. The filter device according to claim 3, characterized in that the end cap (21) has a coaxial connector (47) which extends into the inner filter cavity (43) of the filter element (17) surrounded by a fluid-permeable support pipe (41) and which is engaged by the pipe socket (23) of the element receptacle (5) in the operating position of the filter element (17) and that the connector (47) on its inner wall has the design irregularities (65) which belong to the end cap (21).
 5. The filter device according to claim 4, characterized in that the design irregularities on the pipe socket (23) of the element receptacle (5) have at least one radially projecting rib (63) which runs in the longitudinal direction and to which a depression (65) is assigned which extends in the longitudinal direction in the inner wall of the connector (47) of the end cap (21).
 6. The filter device according to claim 5, characterized in that there are several longitudinal ribs (63) which are distributed around the periphery of the pipe socket (23) of the element receptacle (5) and several depressions (65) assigned to the ribs in the connector (47) of the end cap (21).
 7. The filter device according to claim 6, characterized in that the end cap (21) is composed of an inner sleeve body (45) which is concentric to the longitudinal axis (19), which forms the inner wall of the connector (47) with the depressions (65) located in it, and which is integral with a peripheral annular member which forms the enclosure (37) for the end edge of the filter material (39), and of an outer sleeve (51) which surrounds the sleeve body and whose outside forms a contact surface for the support pipe (41) of the filter element (17).
 8. The filter device according to claim 7, characterized in that the outer sleeve (51) forms a hollow cylinder whose axial length is greater than that of the inner sleeve body (45), so that the inner end edge (53) of the outer sleeve (51) projects over the end edge (55) of the sleeve body (45), and that the end edge (53) of the outer sleeve (51) forms an end part (57) which is drawn radially to the inside, and this end part together with the adjacent end edge (55) of the sleeve body (45) borders an annular groove-like space (59) as a seat for an annular sealing element (61).
 9. The filter device according to claim 3, characterized in that the bottom part (5) which forms the element receptacle on the bottom which faces away from the pipe socket (23) forms a part (71) of a valve housing (71, 73) which is integrally molded on and which has an outlet (75) which can be connected to the tank side of a hydraulic system.
 10. The filter device according to claim 9, characterized in that in the bottom part (5) there is a first fluid passage (77) which leads to a bypass valve (81) located in the valve housing (71, 73) from the dirty side (79) of the filter element (17) which is in the operating position, bypassing the pipe socket (23), and there is a second fluid passage (85) which leads from the pipe socket (23) to at least one other valve (83) located in the valve housing (71, 73), such as an anti-cavitation valve and/or back pressure valve, which valve or valves is or are connected to the outlet (75).
 11. A filter element for use in a filter device according to claim 1, which on at least one end has an end cap (21) which forms an enclosure for a pertinent end edge of the filter material (39) and which can be fixed on an element receptacle (5) which is located in a filter housing (1) for fixing the filter element (17) in its operating position, characterized in that the end cap (21) on parts (47) which engage parts (23) of the element receptacle (5) in the pertinent filter housing (1) is provided with design irregularities (65) which are matched to design irregularities (63) on parts (23) of the element receptacle (5) such that for positional relation of the design irregularities (63, 65), which are aligned to one another, the engagement between the end cap (21) and element receptacle (5) and thus moving the filter element (17) into the operating position are enabled. 